CEN/TC 38

Date: 2024-07-17

prEN 14823:2025

Secretariat: SIS

Biological durability of wood and wood-based products — Quantitative determination of pentachlorophenol in wood — Gas chromatographic method

Biologische Dauerhaftigkeit von Holz und Holzprodukten — Quantitative Bestimmung von Pentachlorphenol in Holz — Gaschromatographische Methode

Durabilité biologique du bois et des matériaux dérivés — Analyse quantitative du pentachlorophénol dans le bois — Méthode par chromatographie en phase gazeuse

CCMC will prepare and attach the official title page.

Contents Page

European foreword 3

Introduction 4

1 Scope 5

2 Normative references 5

3 Terms and definitions 5

4 Safety precautions 5

5 Principle 5

6 Reagents 6

7 Apparatus 6

8 Sampling and preparation of the test sample 7

9 Procedure 7

Table 1 — Example of calibration solutions 8

10 Calculation and expression of results 11

11 Quality assurance 12

12 Test report 12

Annex A (informative) Results of the round robin test 13

Table A.1 – Lab test parameters and individual experimental results 13

Table A.2 – Statistical results 14

Bibliography 15

European foreword

This document (prEN 14823:2025) has been prepared by Technical Committee CEN/TC 38 “Biological durability of wood and wood-based products”, the secretariat of which is held by SIS.

This document is currently submitted to the CEN Enquiry.

This document will supersede the Technical Report CEN/TR 14823:2003, which was fully revised.

Introduction

This document has been issued to facilitate the analysis of pentachlorophenol (PCP) in woods and panels. Pentachlorophenol (PCP) can be present as residues from old anti-sapstain treatment.

The EN status was adopted by the CEN/TC 38, considering the need of a European standard dealing with this topic in particular for the wooden construction products such as wood-based panels or floorings, which are concerned by a pentachlorophenol (PCP) content required by harmonized standards for the Construction Product regulation.

This document specifies a laboratory method of determining the pentachlorophenol content of wood. The method is applicable to all types of pentachlorophenol (PCP) in woods and wood-based materials as well as for the analysis of waste timber with respect to its pentachlorophenol (PCP) content.

The method described has a measurement range from 250 µg/kg up to pentachlorophenol (PCP) contents of 5 mg/kg of dry matter. These figures refer to the given example (where an aliquot of 1 ml of the extract is used for acetylation, see 9.3).

NOTE 1 If lower quantification limits are required, a higher volume of extract aliquot can be used for derivatisation.

NOTE 2 This method could have some modifications with some wood species as hardwoods. In general, in the case of complex matrix, a method using mass spectrometry can be used.

The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

EN 212, Wood preservatives — General guidance on sampling and preparation for analysis of wood preservatives and treated timber

EN 351-2, Durability of wood and wood-based products — Preservative-treated solid wood — Part 2: Guidance on sampling for the analysis of preservative-treated wood

EN ISO 3696, Water for analytical laboratory use — Specification and test methods (ISO 3696:1987)

No terms and definitions are listed in this document.

Persons using this method should be familiar with normal analytical laboratory procedures and practice.

This method does not purport to address all the safety problems, if any, associated with its use.

It is the responsibility of the user to establish safety and health practices and to ensure compliance with any European or national regulatory conditions.

Pentachlorophenol is extracted from the wood material using appropriate solvents. The extracted pentachlorophenol is transformed to pentachlorophenol acetate by derivatisation of an aliquot of the extract in aqueous potassium carbonate solution with acetic anhydride. The acetate derivative formed is extracted from this aqueous solution with n-hexane and analysed by gas chromatography with electron capture detection or mass selective detection.

Methanol, acetone or toluene are considered as convenient. Other solvents can be used. Some extraction difficulties can occur with some wood species (e.g. hardwoods). It is recommended to crosscheck the extraction efficiency of any other solvent or solvent mixture.

For complex mixtures, the method using mass spectrometry should be used.

During the analysis, unless otherwise specified, use only reagents of recognized analytical grade, which have been checked in advance as to not interfere with the analytical results, and water complying with grade 3 as defined in EN ISO 3696.

6.1 Acetic anhydride (C4H6O3).

6.2 Methanol (CH3OH).

6.3 Acetone (C3H6O).

6.4 Toluene (C6H5CH3).

6.5 n-Hexane (C6H14).

6.6 Potassium carbonate, solution, c(K2CO3) = 0,1 mol/l.

6.7 Sodium sulfate, anhydrous (Na2SO4).

6.8 Pentachlorophenol (pentachlorophenol (PCP), (C6Cl5OH)) of GC quality.

6.9 2,4,6-tribromophenol (TBP, (C6H2Br3OH)) of GC quality as an internal standard.

6.10 Certified Reference Material BCR-683 (PCP and PAH in wood).

6.11 Certified Reference Material BAM-U030 (PCP in wood).

Ordinary laboratory apparatus and the following.

Glassware should be thoroughly cleaned prior to use.

7.1 Analytical balance, accurate to 0,1 mg.

7.2 Ultra-sonic bath equipped with a thermostat capable of controlling and maintaining a temperature of 40 °C.

7.3 Pressurized fluid extraction (PFE) system.

Pressurized fluid extraction (PFE) is an automated extraction technique that uses elevated temperature and pressure.

7.4 Separating funnel.

7.5 Disposable Pasteur pipettes made of glass.

7.6 Volumetric pipettes.

7.7 Microlitre syringes.

7.8 Volumetric flasks.

7.9 Conical flasks, with screw caps provided with an insert of polytetrafluoroethylene (PTFE) or alternatively with standard ground stoppers provided with PTFE standard ground sockets and conical joint clips.

7.10 Extraction cell for PFE system.

7.11 Gas chromatograph equipped with a non-discriminating injection system and an electron capture detector (ECD) or mass spectrometry (MS), with split/ splitless injector.

7.12 Separation column. Capillary column, with stationary phase of (5 %-Phenyl)-methylpolysiloxane.

NOTE Pre-column coated with deactivated silica could be used.

Samples submitted to testing shall be prepared and conditioned in accordance with EN 351-2, EN 212, or another suitable standard depending on the aim of the test, in particular the cutting area (sawdust or shaving).

Collect at least 5 to 10 g of the sample material taken according to e.g. EN 212. This sample material is obtained with the appropriate cutting tools, thoroughly cleaned with acetone for example.

This sample material is cut by plane to shavings or ground under mild conditions (to avoid heating) to sawdust with an approximate particle size ≤ 2,0 mm diameter.

Homogenize the ground sample material to obtain a representative sample and store it in a brown glass vessel with screw caps with a PTFE insert. This is the test sample.

The mass submitted to test could be lower according to the shape and the type of the material tested.

The analysis is carried out on duplicate. If results differ by more than 15 % an additional analysis shall be carried out.

Prepare or procure a standard solution containing the compounds in appropriate concentration depending on the sensitivity of the system and the conditions diluted in an analytical solvent for chromatography. By example:

Prepare the stock solutions by weighing about 12,5 mg of pentachlorophenol (PCP) (6.8) and TBP (6.9) separately to the nearest of 0,01 mg and dissolve each in 25 ml methanol (6.2).

NOTE 1 These stock solutions with nominal concentrations of 0,5 mg/ml can be stored in the dark at –18 °C for three months.

Given sufficient solubility and stability, the standard stock solution can be dissolved in other solvent than methanol. Acetone and toluene are considered as suitable.

Transfer by pipette (7.6) 1,00 ml of stock pentachlorophenol (PCP) solution (9.2.1) to a 10 ml one-mark volumetric flask (7.8) and make up to the mark with methanol (6.2) to give a solution having a nominal concentration of 50 µg/ml pentachlorophenol (PCP). Repeat with the TBP stock solution to give a solution having a nominal concentration of 50 µg/ml TBP.

NOTE 1 The maximum storage time of these solutions is one month at approximately 5 °C, e.g. in a refrigerator.

Given sufficient solubility and stability, the working solutions can be dissolved in other solvent than methanol. Acetone and toluene are considered as suitable.

To a series of 100 ml one-mark volumetric flasks (7.8), transfer 25 µl, 50 µl, 100 µl, 250 µl and 500 µl of pentachlorophenol (PCP) working solution (9.2.2). To each of the five flasks and one with no added pentachlorophenol (PCP), add 250 µl of TBP working solution (9.2.2) and make up to the mark with methanol (6.2). A series of standards containing 0,0 µg, 1,25 µg, 2,5 µg, 5 µg, 12,5 µg and 25 µg of pentachlorophenol (PCP), with 12,5 µg TBP as internal standard in each, is thus obtained. The concentration of calibration solutions in methanol is given in Table 1.

Table 1 — Example of calibration solutions

NOTE 1 The concentration of the calibration solutions as well as the volume of the aliquot of the extract taken for acetylation can be varied to cover the expected level of pentachlorophenol (PCP) contamination of the wood sample up to at least 5 mg/kg.

Given sufficient solubility and stability, the working solutions can be dissolved in other solvent than methanol. Acetone and toluene are considered as suitable.

Add 30 ± 1 ml of the potassium carbonate solution (6.6) to a series of six separating funnels (7.4). Using a pipette (7.5), transfer 1 ml of each standard solution (9.2.3) to its allotted separating funnel, shake to mix the contents of the separating funnel thoroughly. To each separating funnel, add 2 ± 0,2 ml of the acetic anhydride (6.1) and shake the mixture for 2 min. Extract the acetylated pentachlorophenol and tribromophenol with 10 ml of the n-hexane (6.5) by shaking the mixture for 10 min. By means of a clean Pasteur pipette (7.5), transfer the upper (organic) layer into a 25 ml one-mark volumetric flask (7.8) via filter funnel fitted with a filter paper containing anhydrous sodium sulfate (6.7) or a hydrophobic phase separator filter. Repeat the extraction with another 10 ml quantity of n-hexane and wash the filter paper and sodium sulfate with small quantities of n-hexane. Make up to the mark with n-hexane.

The standard solution without PCP (9.2.3) should be included as an acetylation blank.

Depending on the expected pentachlorophenol (PCP) content, weigh, to the nearest 0,1 mg, 1 g to 5 g of the test sample (Clause 8) and transfer to a conical flask (7.9) or an extraction cell (7.10). Add (under gravimetric control) 125 µl (see note 1) of the TBP working solution (9.2.2) to the test sample, close the flask with the screw cap. Let this solution soak for 30 min.

Two extraction modes are the possible:

- By ultra-sonic bath (7.2):

Add 50 ml of solvent to the flask and swirl to ensure that all the wood is wetted. Place the flask in an ultra-sonic bath (7.2) for 1 to 2 h at 40°C. After the solids have settled, the extract (approximatively 25 ml) is carefully removed with a volumetric pipette (7.6) and/or a Pasteur pipette (7.5), transferred to a sealable glass vessel such as a 50 ml one-mark volumetric flask (7.8) and stored for further processing.

- By pressurized fluid extraction (7.3):

Use 22 ml cells (7.10) for extraction with the device (7.3). Carry out solid/liquid extraction with solvent. The extract is transferred into a 50 ml volumetric flask (7.8). Complete to the line with solvent.

This assumes that 1 ml of the extract will be taken for analysis. If a greater volume, for example, 5 ml is to be taken, 50 µl of the 50 µg/ml working solution should be taken (compare to 9.2.3).

Other extraction techniques, like Soxhlet extraction and microwave assisted extraction, can be suitable. However, when using other extraction techniques, the comparability to the herein described methods should be demonstrated, e.g. by using a certified reference material (CRM).

Methanol and acetone are considered as convenient. Other extraction solvents can be suitable like toluene. If nonpolar solvents are used (like toluene or hexane) for wood extraction (9.3.1) and calibration solutions (9.2.3), the liquid extraction as described in 9.2.4 is redundant. However, when using other extraction techniques, the comparability should be demonstrated.

Follow the procedure given in 9.2.4

A higher volume of the aliquot of the extract can be used for derivatisation if a quantification limit below a content of 250 µg pentachlorophenol (PCP) per kilogram of wood dry matter is required (see Clause 1).

Guidance on the gas chromatographic conditions is given in the following:

For laboratories with less experience in this method it is advisable to check the recovery of the acetylated TBP internal standard while analysing the wood material by using an additional internal standard such as PCB 52 (2, 2’, 5, 5’-tetrachlorobiphenyl – m/z 292/290/220). It can be added to the final solution which is filled to the mark with n-hexane. In this way the absence of any interference in the position of the internal standard in the chromatogram can also be checked.

Please consult the user instructions of the manufacturer for optimal GC conditions. Please check if the chromatograph is equipped with a gas filter as it is needed for the trace analysis of volatile environmental pollutants.

A guidance of oven temperature programme is given: 50°C (1 min); 50°C to 160°C at 20°C/min; 160°C to 310°C at 8°C/min and 310°C for 5 min.

By use of some injection techniques interference can occur caused by substances extracted from the wood matrix. In such cases it is recommended to perform an additional clean-up procedure (e.g. by silica gel) to improve the chromatographic performance.

The calibration is carried out using the internal standard method.

The linear calibration function is based at least on five calibration points as described in (9.2.3) and the determination of pentachlorophenol (PCP) based on this function is described in the following. This calibration function includes the whole analytical procedure. It is established by plotting the ratio of the peak area of the acetylated pentachlorophenol (PCP) standard to that of the acetylated TBP standard versus the relating ratio of concentrations according to the following equation:

where:

Laboratory quality checks

An appropriate level of quality control shall be employed and documented. Method performance checks shall include:

a) The validity of the calibration function shall be checked within each batch of samples by analysis of calibration solutions as unknown analytical samples (e.g. two for every ten samples). If the linear function calculated from these control measurements falls within the 95 % confidence interval of the actual calibration function this function is assumed to be valid. If not, a new calibration function shall be established.

A Quality Control (QC) should be added to validate calibration. The QC procedure can be a set of calibration solutions from another supplier.

b) The linear regression coefficient (r2) shall be above 0.985.

c) Within each series of test samples to be analysed, a blank measurement of the whole analytical procedure shall be carried out.

Use of the Certified Reference Material

A Certified Reference Material (CRM) could be used at each analytical sequence (6.10) (6.11).

Other CRM in wood could be used.

The pentachlorophenol (PCP) content w, in milligrams per kilogram of the test sample is calculated from this multiple point linear calibration function (9.3) using the following equation:

where:

The pentachlorophenol (PCP) content w of the test sample is given in milligrams per kilogram of dry matter as the mean of independent determinations together with its measurement uncertainty.

The analysis is carried out on duplicate. The final result is the mean of both analysis.

If results differ by more than 15 %, an additional analysis shall be carried out. The final result is then the mean between the three replicates.

The accuracy and repeatability of the measuring method are important factors, which shall be determined to evaluate the results and the suitability of the method for the intended purposes. This method was validated in a laboratory intercomparison with 4 participating laboratories for three test samples at different levels of pentachlorophenol (PCP) contamination. The performance characteristics of the intercomparison were evaluated and the repeatability and the reproducibility were determined. A summary of the intercomparison data are given in Annex A.

The test report shall contain the following information:

a) A reference to this document;

b) The date of sampling;

c) The sampling procedure;

d) The date of testing;

e) The preparation procedure;

f) The extraction procedure;

g) The analytical procedure;

h) Individual results and calculated mean.

1. 
   (informative)
   
   Results of the round robin test

Four laboratories took part in an interlaboratory study for the quantitative determination of pentachlorophenol in wood. Two wood samples were tested:

- Sample 1: CRM BCR 683 (Beech wood - certified concentration of 3.6 ± 0.5 mg/kg on dry mass)

- Sample 2: CRM BAM U030 (mix North American pine wood industrially treated with PCP and untreated Beech wood, certified concentration of 7.17 ± 0.80 mg/kg at a water content of 6.95 ± 0.05 %)

The principles described in prEN 1483 were applied. Three replicates per sample were carried out. Main test parameters and experimental results are presented in Table A.1.

Table A.1 — Lab test parameters and individual experimental results

Statistical results (mean, trueness, precision (repeatability, reproducibility), first approach of expanded uncertainty) are summarized in Table A.2.

Table A.2 — Statistical results

NOTE For sample 2, certified value is not in dry mass. Each individual concentration was recalculated in relation with its sample intake (using moisture content of the sample).

Bibliography

[1] BS 5666, Part 6 (1983) Methods of analysis of wood preservatives and treated timber, Part 6, Quantitative analysis of preservative solutions and treated timber containing pentachlorophenol, pentachlorophenyl laurate, γ-hexachlorocyclohexane and dieldrin, British Standards Institute, London

[2] AWPA Standard A-5 Standard methods for analysis of oil-borne preservatives (1999) American Wood Preservers’ Association, Book of Standards 1999

[3] ISO 5725‑1, Accuracy (trueness and precision) of measurement methods and results — Part 1: General principles and definitions

[4] REGULATION (EU) No 2024/3110 OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 27 November 2024 laying down harmonised rules for the marketing of construction products and repealing Regulation (EU) No 305/2011

[5] EN 13986, Wood-based panels for use in construction – Characteristics, evaluation of conformity and marking

[6] EN 14342, Wood flooring and parquet — Characteristics, evaluation of conformity and marking

[7] EN 14915, Solid wood panelling and cladding — Characteristics, requirements and marking

[8] EN 14041, Resilient, textile, laminate and modular multilayer floor coverings — Essential characteristics

[9] EN 351-1, Durability of wood and wood-based products — Preservative-treated solid wood — Part 1: Classification of preservative penetration and retention

[10] EN 322, Wood-based panels — Determination of moisture content

[11] EN 13183-1, Moisture content of a piece of sawn timber — Part 1: Determination by oven dry method

[12] ISO 5725-2, Accuracy (trueness and precision) of measurement methods and results – Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method

[13] ISO 11465, Soil quality – Determination of dry matter and water content on a mass basis – Gravimetric method